Relieved Ford V8 block

[Ian NZ]

Is it better to have a relieved Ford V8 block for a high performance Flathead V8 motor and is a twin spark plug head any advantage over a single plug head and where should the plugs be positioned.

[JSeery]

All of this depends on the engine size and intended use. For a street engine there is very little gain with either modification. The reason being they are not beneficial until you get into the higher RPM range.

[Ian NZ]

Originally Posted by JSeery

All of this depends on the engine size and intended use. For a street engine there is very little gain with either modification. The reason being they are not beneficial until you get into the higher RPM range.

This would be for a super charged flat head engine for the Bonneville salt flats. The heads would have no water jackets .

[JSeery]

Well, that is a different animal! There are some Bonneville guys here on the Barn that my chime in.

[Pete]

Originally Posted by Ian NZ

This would be for a super charged flat head engine for the Bonneville salt flats. The heads would have no water jackets .

No water will work fine at the drags.
Probably not so good at Bonneville.

The engine will have to run over a minute at full throttle.
If you think you can make it work, try it on the dyno but stay out of the room when testing.

A relief works good on a race engine.
Dual plugs are not necessary. Marginal if any gain.

[40 Deluxe]

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Relieving drops the compression, which causes slower throttle response. Not good for a street engine! Also, think of air flow into a flathead engine: The air/fuel mixture flows upward through the intake valve, then has to do an abrupt, almost 180 deg. turn to fill the cylinder. Air has weight, so therefore has inertia, meaning it wants to keep flowing up from the valve. Obviously, the head forces it to turn. So the majority of the flow follows the head surface around into the cylinder. Thus, flow through that ditch you just ground into the deck surface will be small at the RPM levels of a street engine. I think it's a bad tradeoff to give up compression for slight improvements in high RPM airflow unless it's an all-out race only engine.

[flatheadmurre]

For supercharged you want flow...so a larger transfer area is good.
For an engine like that takeoff/torque isn´t so interesting...you are chasing that last bit of horsepower...backing off just a notch to keep the engine from blowing up.
Running competition you will be aiming for a modern computer controlled ignition system...no need for twinplugs.
Good luck on setting a score !

[JWL]

Radical porting can be avoided with a supercharger and head design/revisions are much more important than any block relief.

Even with the block or heads "O"-Ringed there will be a limit to the CR (compression ratio) the engine can withstand. This lends itself to making desirable combustion chamber modifications.

I never saw any power improvements with dual plugs but never tried them with boost pressure. I think the plugs should be in the transfer area, clear of the valves, and biased to the exhaust side.

The Bonneville rules do not allow modern computer ignition systems in the Vintage Engine classes.

[Flathead Fever]

The best reason to relieve the block is for when you driving down the road with your flathead singing the Little Deuce Coupe song, "Ported and Relieved and its Stroked and Bored". Its not going to sound as good if your only singing, "Ported and its Stroked and Bored" The words FLOW better when its relieved.

59L blocks which are suppose be truck engines were relieved. I've heard all kinds of theory's on why they did this. To prevent the blocks from cracking is one. That does not make any since, why would you remove metal to prevent it from cracking? Better flow for more power in the trucks. If it made more power why would you not do it to all the flathead blocks? That does not make since to me either. I have never read this anywhere, its my own personal theory. The "L" in 59L could have been for "low compression"? Maybe the trucks need a lower compression ratio to prevent detonation under heavy loads. That makes the most since to me.

I bought a 59L to get a factory relieved block. Removed the heads and it was not relieved. Just my luck.

I'm not sure relieving a block on a street engine helps. You probably loose more power from the compression you loose than the benefit of increased air flow. I talked with Tony Baron about it and he said they ran all kinds of flow bench tests. He said if you are going to relieve the block just taper the relief from the valve up to the top of the cylinder rather than relieving the whole area out. That's what I have decided to do with my engine project.

One consideration rather to relieve a block or not will be the heads you use. Originally some of the manufacturers made two different style heads. A "race" head" which is thicker, requires longer studs and the compression ratio was calculated assuming you were relieving the block. Then there was the "street head". It could use the original studs, and was not as thick as the "race heads". It was designed to be used on a stock block that was not relieved.

.

[Krylon32]

It's been a while but I was fortunate to purchase 2 new 59L relieved blocks still covered in cosmoline in factory crates. I always thought since we had 2 military bases in the area they were surplus? I built the first one with a 4 inch crank, mild cam, Chevy valves, Egge pistons, Offenhauser heads and 2 94's and put it in a 32 Ford roadster and it was a good running street motor. The second one I did about the same but with a Road Runner blower and man did that light that engine up. Installed it in another 32 roadster with a 5 speed and it was a rocket. I'll probably never find another new block like these.

[Ol' Ron]

I did some flow testing with combustion chambers and found the transfer area to be the only place flow could be improved. Relieving the block only improved flow if the transfer area was very low to increase compression. The best chamber was with a 10 degree angle of the transfer area with a 60 deg exit. Unfortunately this lowers compression. JWL put me on to the EAB head which is close to this. so just improving the exit of the relief woll accomplish the same thing. Re shaping the chamber in a new casting could increase the CR with out affecting flow. I made up some wooden chambers for testing. Have some pics, will try to find them.

[Ronnieroadster]

Originally Posted by Ian NZ

This would be for a super charged flat head engine for the Bonneville salt flats. The heads would have no water jackets .

Ian all of my runs at the Bonneville saltflats with my flathead Ford block has been with supercharging. Your idea of running no water in the heads as Pete wrote will take a lot of thought. I have a few questions on what your combination will be.
1- Are you running alcohol or gas?
2- Injection or carburation?
3- Class you plan on running?
4- Blower type
Theres lots more to ask but first let me see what your answers are for the above questions.
Ronnieroadster

[Pete]

“Radical porting can be avoided with a supercharger”

> Yes, if you are lazy and do not like breathing cast iron and rust that goes
along with doing that job.
With any flathead, bigger is better for more power.

“and head design/revisions are much more important than any block relief.”

> Head revisions are extremely important but most people avoid the ones that
make the most difference because of the expense. This is one of the big
reasons why most street engines are limited to the 150 hp range.
Just about ANY combination of relief, head transfer area and dome can be
made to make this kind of power.
One thing will always be true, no matter what the engine is used for, the
deeper the relief, the more power it will make.

“Even with the block or heads "O"-Ringed there will be a limit to the CR (compression ratio) the engine can withstand.”

> True. A street engine does not need compression over about 8 to 1 what with
the poor quality gas we have now. 10 or 11 to 1 will work fine with water
injection but most people do not want to bother filling a water tank every
few miles.
As far as high compression in a race engine, we have been running 14 to 1
naturally aspirated with no problems for many years. It is very easy to get
compression in a 321 or 334 ci engine. Not so much in a typical small size
street engine.

“This lends itself to making desirable combustion chamber modifications.”

> As noted above, mods that make the most difference are usually too
expensive for the average person with no shop facilities.

“I never saw any power improvements with dual plugs but never tried them with boost pressure. I think the plugs should be in the transfer area, clear of the valves, and biased to the exhaust side.

The Bonneville rules do not allow modern computer ignition systems in the Vintage Engine classes.”

> Lucky we have mods to vintage mags that will give us 10 amps. That's
enough to light any amount of the "can" you might want tp pour.

[supereal]

At our shop we have seen blocks ruined by poorly done "relieving'. The last one had been cut down so far the top piston ping was exposed! For usual driving, porting and relieving
isn't worth the effort in terms of improved performance.

[Tim Ayers]

The 5th and final block that I tore down to use for my current engine was a 59L with factory relief. It's interesting for that cut was pretty crude when inspected up close.

As noted in another post, it will be a 297 c.i. and the plan is to get 8-1 compression.

I've always liked the look of those dual plug heads. There are two different designs that I've seen. Side by side like the heads in the OP picture and aligned vertically. Curious how the placement of the dual plugs makes a difference.

I think some Eddie Meyer heads were cast with a "boss" to allow someone to weld up the stock, centrally located plug location and tap two new ones.

[Ol' Ron]

My friend George has a set of Elco heads which has a vertical set of plugs. We made a front timing cover to handle 2 distributors. Preliminary testing doesn't show much improvement. However we're having other problems, so we don't have enough information to make a comment. Engine runs just as well on either dist.

[glennpm]

Great having your vast experience on this site Ron. Big thanks!!


Glenn

[rotorwrench]

I figure if a person has an old relieved truck block, they might as well make the best of it. Clean the squarish contours up & round it off like what they did back in the day and run the old crow foot type aluminum heads. Those chamber shapes were made for the reliefs since they were so popular back in the day.

[Ian NZ]

Is there any advantage of having the plugs high up on the heads of a supercharged V8 engine as per photo.

[tubman]

I would be veeery interested on how that particular engine runs. On first glance, those plug locations don't look good to me.